The present disclosure relates generally to actuators for use in a heating, ventilating, or air conditioning (HVAC) system and more particularly to systems and methods for determining the position of HVAC actuators.
HVAC actuators are used to operate a wide variety of HVAC components such as air dampers, fluid valves, air handling units, and other components that are typically used in HVAC systems. For example, an actuator may be coupled to a damper in a HVAC system and may be used to drive the damper between an open position and a closed position. A HVAC actuator typically includes a motor and a drive device (e.g., a hub, a gear train, etc.) that is driven by the motor and coupled to the HVAC component.
HVAC actuators typically require accurate position feedback for use in closed-loop control systems. Some HVAC actuators use resistive potentiometers to measure actuator position. For example, a sliding component of the resistive potentiometer may be coupled to the gear train of the actuator such that a change in actuator position causes a corresponding change in the resistance of the potentiometer. Resistive potentiometers typically require a physical connection to the gear train and are therefore susceptible to wear and degradation as the actuator moves between positions.
Other HVAC actuators use Hall effect sensors to measure actuator position. For example, one or more permanent magnets may be coupled to the gear train of the actuator such that a change in actuator position causes the permanent magnets to move past the Hall effect sensors. The Hall effect sensors provide an output to an electronic circuit, which records a count each time a magnet moves past a Hall effect sensor. Each count may correspond to a known change in actuator position (e.g., 0.1 degrees per count).
One disadvantage of using Hall effect sensors to measure actuator position is that power is required to monitor feedback from the Hall effect sensors. If the actuator position is changed when the actuator is not powered (e.g., a user manually moving the actuator), the electronic circuit is unable to record the sensor counts and cannot track the change in actuator position. It would be desirable to provide a system and method for determining actuator position that overcomes the disadvantages of conventional position sensing techniques.